Process for dyeing durable press cellulosic fabrics with basic dyes

ABSTRACT

DURABLE-PRESS CELLULOSIC FABRICS HAVE BEEN PREPARED IN A PROCESS WHICH SIMULTANEOUSLY RENDERS THEM RESPONSIVE TO BASIC DYES. IN A TWO-PHASE PROCESS THE CELLULOSIC COMPONENT IS CROSSLINKED USING A CROSSLINKING AGENT AND AN ALPHA-HYDROXY CARBOXYLIC ACID IN THE FIRST PHASE (THE CARBOXYLIC ACIDS SERVING THE DUAL PURPOSE OF CATALYST AND REACTIVE ADDITIVE), THUS PRODUCING A CROSSLINKED CELLULOSIC FABRIC WITH PENDANT CARBOXYLIC GROUPS. IN THE SECOND PHASE, A BASIC DYE IS SELECTIVELY ABSORBED BY THE CHEMICALLY MODIFIED CELLULOSIC TEXTILE, DUE TO THE PRESENCE OF THE CRABOXYLIC GROUPS.

3,788,804 PROCESS FOR DYEING DURABLE PRESS CELLULOS'IC FABRICS WITHBASIC DYES Robert J. Harper, Jr., and Gloria A. Gautreaux, Metairie,

and Joseph S. Bruno, Chalmette, La., and Matthew J. Donoghue, Knoxville,Tenn., assignors to the United States of America as represented by theSecretary of Agriculture No Drawing. Filed Mar. 28, 1972, Ser. No.238,947

Int. Cl. D06p /00 US. Cl. 8-18 9 Claims ABSTRACT OF THE DISCLOSUREDurable-press cellulosic fabrics have been prepared in a process whichsimultaneously renders them responsive to basic dyes. In a two-phaseprocess the cellulosic component is crosslinked using a crosslinkingagent and an alpha-hydroxy carboxylic acid in the first phase (thecarboxylic acids serving the dual purpose of catalyst and reactiveadditive), thus producing a crosslinked cellulosic fabric with pendantcarboxylic groups. In the second phase, a basic dye is selectivelyabsorbed by the chemically modified cellulosic textile, due to thepresence of the carboxylic groups.

A non-exclusive, irrevocable, royalty-free license in the inventionherein described, throughout the world for all purposes of the UnitedStates Government, with the power to grant sublicenses for suchpurposes, is hereby granted to the Government of the United States ofAmerica.

This invention relates to chemical treatments which impart wrinkleresistance to cellulosic textiles. Specifically, this invention relatesto chemical treatments to cellulosic textiles to render them wrinkleresistant as well as highly receptive to basic dyes. In addition to theimproved dye receptivity imparted by the new process considerableimprovement in certain other properties, such as tearing strength andmoisture regain, can be achieved.

This invention also relates to the use of alpha-hydroxycarboxylic acidsas crosslinking catalysts in finishing. The normal catalyst used incrosslinking cotton is a metal salt catalyst such as magnesium chlorideor zinc nitrate.

Another catalyst which has found considerable use is the mixed catalystsystem. This so-called mixed catalyst is a complex formed by thecombination of a metal salt and a hydroxy acid such as magnesiumchloride-citric acid. This complex catalyst is a very powerful catalystand small concentrations are sufiicient to promote the desiredcrosslinking of the fabric.

The catalysts used for this work are the hydroxy acids themselveswithout any metal salt additive. Because these hydroxy acids arerelatively weak acids, large amounts can be used to promote the desiredcrosslinking of the fabric. The objective of the use of large amounts(2-10%) is that this permits a significant quantity of these agents tobe grafted onto the fabric. The reason that this occurs is that thehydroxyl group of the hydroxy acid is reactive with the N-methylolmoiety of the crosslinking agent. When another N-methylol group of thecrosslinking agent reacts with cotton the hydroxy acid then becomesattached to cotton. In this respect, an agent such as dimethyloldihydroxyethyleneurea is a particularly effective crosslinking agentbecause it has four N- methylol groups available for the grafting of thehydroxy acids or available for crosslinking. As a result of using thisagent and the hydroxy acid in finishing, one obtains a crosslinkedfabric with high conditioned wrinkle re- United States Patent 0 covery,good durable press rating and a titratable amount I ice of carboxylgroup on the fabric. This carboxyl concentration (up to 1.9% dependingupon acid type and concentration of acid used in the finishing bath)gives the fabric a potential acidic character.

Thus, one should consider three fabrics. One fabric is the untreatedcotton, the second is a fabric crosslinked in a conventional manner witha metal salt catalyst, and the third was crosslinked using a hydroxycarboxylic acid as the catalyst. Examples of such hydroxy-carboxylicacids are glycolic acid, lactic acid, mandelic acid, tropic acid,tartaric acid, and malic acid. To permit dyeing of ese fabrics, thesamples are treated with dilute hydrochloric acid to convert the pendantcarboxyl groups from the salt form to the acid form. Then, the fabricsare washed with distilled water several times and dried (optional).(This pretreatment may be omitted depending upon dye bath and dyestulfsubsequently employed.) The fabrics are then dyed in a dye bathcontaining a basic dyestuif and the other normal reagents commonly foundin a basic dye bath. After the fabrics are dyed in the normal manner,the resultant fabrics are rinsed and laundered. While the untreatedcotton and the cotton crosslinked with the metal salt catalyst have pooraffinity for the basic dyestuff, the samples of fabric containing thecarboxyl groups are dyed a significantly deeper color. Examples of sometypical basic dyes with which this approach has found merit are C.I.(Color Index) Basic Blue 11, (CI. 44040), C.I. Basic Violet 10 (Cl.45170). and Cl. Basic Violet 1 (Cl. 42535).

In addition to dyeing the fabric with an acidic character with the basicdye, it is also possible to dye with a basic dye a fabric in which theacid grouping has been converted to the salt form. This techniqueinvolves the replacement of the proton on metal salt (for example sodiumcarboxylate) with the ammonium or quaternary or hydrochloride form ofthe basic dye. This technique has been used with methylene blue chloride(salt Basic Blue 9 CI. 52015).

By contrast, the fabric crosslinked in the normal manner shows poor dyereceptivity. This is true not only of the basic dyes used in this workbut for other types of cotton dyes as well. The option of being able todye after fabric has been crosslinked may have certain distinctmarketing, processing, and technical advantages. First, it would bepossible to dye white goods a different color should a demand arise forspecial colored fabrics. Such an option of selling fabrics either whiteor colored might be advantageous for inventory control. Second, due tothe high temperatures commonly used in textile finishing, thesublimation of dyestuffs means that certain bright shades might not bereadily available. Also, the effects of metal salt catalysts and heat toimproper shade change might be easily corrected if fabric could be dyedafter crosslinking. The fact that these fabrics could be dyed afterfinishing adds an element of flexibility that is not currently availableeither in processing conditions or choice of dyestuff. Finally, it wouldbe possible to adjust fabric colors should any undesirable shade changesoccur in curing or other steps. In addition to the dyeingcharacteristics of these fabrics, the use of these mild acid catalystsenhances certain other fabric properties. First, the fabrics usuallyhave a higher level of tearing strength retention. Second, moistureregain of the fabric is usually increased. Increased moisture regain isusually associated with improved comfort characteristics. Third, thefabrics usually show improved soil release performance due to thepresence of the carboxylic groups which are permanently cross-linkedinto the fabric.

In general terms, the process of this invention starts with theincorporation of the hydroxy acid in a normal pad bath solution insteadof the metal salt latent acid normally used in such solutions to producewash-wear or durable press cottons. From this point on, fabric isfinished in a standard manner according to contemporary textilepractice. This method can be used with a number of textile formulations,the only requirement being that the metal salt catalyst and theappropriate amount of water be replaced by the hydroxy acid catalyst.The method is readily applicable to either precure or postcure onebath,one-step treatments. The fabric is washed and then dyed with a basic dyeutilizing normal dyestufi practices.

DESCRIPTION OF AGENTS A number of hydroxy acids has been employed as thehydroxy acid catalyst. Typical of such agents are lactic acid (A),glycolic acid (B), tartaric acid (C), mandelic acid (D), malic acid (E),citric acid (F), mucic acid (G), and tropic acid (H). In general, themethod would seem feasible to almost any formulation containing ahydroxy carboxylic acid or its salt.

Examples of suitable hydroxy acids are the following:

Concentration of agent in pad bath solution While a quantity of aboutfrom 0.5% to 10% of the various acids have been shown to be effective inpromoting an adequate fabric cure, the carboxyl content of the fabricincreases progressively with the use of larger amounts of hydroxy acidin the finishing bath. For the purposes of maximizing carboxyl contentas well as because of economic considerations a concentration of acidranging from about 2% to about 5%seems to be about the optimumconcentration for the acid catalysts and coreactant.

To summarize, the invention can best be described as a process forimparting receptivity for basic dyes to crosslinked cotton fabrics. Thisimprovement consists of the use of hydroxy acids as catalysts forcrosslinking systems as well as coreactants to lead to crosslinkedfabrics containing pendant carboxyl groups. Due to the presence of thesecarboxyl groups, dye procedures can now be applied to these fabricsusing basic dyes, which would be substantive to an acid substrate.Neither cotton crosslinked in the normal manner nor untreated cottonfabrics have good substantitivity for basic dyestulfs.

Only the basic formulations have been used in the examples. Variationsusing softeners, wetting agents, and

polymer additives are readily accessible in the art of textilefinishing.

EXAMPLE 1 Cotton printcloth was padded with a solution containing 9parts dimethylol dihydroxyethyleneurea, 0.5 part zinc nitratehexahydrate, and 90.5 parts of water. The fabric was dried for 7 minutesat 60 C. and cured for 5 minutes at 160 C. The fabric was then launderedand tumble dried. A second sample of. cotton printcloth was padded with9 parts dimethylol dihydroxyethyleneurea, 2 parts glycolic acid and 89parts water. The sample was then dried, cured and washed in the samemanner as the first sample. In addition to these samples, other sampleswere treated with 9 parts dimethylol dihydroxyethyleneurea, varyingamounts of hydroxy acids and sufficient water to total 100 parts or100%. The amounts of the acids and the properties of the resultantfabrics are listed in Table I. It can be seen that the elfect of thesetreatments is to produce fabrics with high resilliency (wrinklerecovery) like a conventional durable press fabric [sample crosslinkedwith dimethylol dihydroxyethyleneurea (DMDHEU) using zinc nitratecatalyst]. However, an improvement of approximately 50-150 g. in warptearing strength is usually observed. Furthermore, an increase inmoisture regain from 0.3% to 1.4% higher than the crosslinked controlwas achieved. Increased moisture regain is generally associated withimproved comfort characteristics. Finally, titration indicated asubstantial increase in the carboxyl content of these crosslinkedfabrics. Because of this increase in carboxyl content, the fabric nowpossesses an acid character which may have advantages for specificapplication purposes.

for anyone skilled TABLE I.PROPERTIES 0F FABRICS CROSSLINKED USINGHYDROXY ACID CATALYSTS Warp Cond. tearing Percent WRA strength Percentmoisture Acid catalyst (deg) (g.) COOH regain 0.5% Zl1(NO3)2-6Hz0 285387 0. 25 3.8 2.0% glycolic acid- 287 493 0. 81 4. 1 3.0% glycolic acid.281 440 1. 06 4. 1 4.0% glycolic acid. 277 421 1. 32 4. 3 5.0% glycolica 269 433 1. 4G 4. 5 2.0% malic acid 287 507 0.60 4.0% malic acid--. 294480 1.20 2.0% mandelic aci 276 540 0. 43 4. 9 4.0% mandelic acid- 275527 0.61 4. 9 6.0% mandelic acid- 276 507 0.91 5. 0 2.0% lactic acid 273533 4.0% lactic acid 269 10.0% lactic acid 268 433 0.5% citric acid- 280487 0. 50 5. 3 1.0% citric acid- 279 500 0. 49 4. 8 2.0% citric acid 289480 0. 83 4. 6 4.0% citric acid- 294 433 1. 36 4. 6 6.0% citric acid 297427 1. 85 4. 7 1.0% tartaric ac1d 274 393 0. 55 5. 0 2.0% tartaric acid.278 373 0. 69 5. 2 4.0% tartaric acid. 273 327 1.22 5. 1 3.0% tropicacid- 256 573 0. 51 5. 4

EXAMPLE 2 Swatches of the samples listed in Table I were immersed in 1%hydrochloric acid for about 30 minutes. They were, then, repeatedlywashed with distilled water. After these samples were dried, they wereimmersed in a dye bath prepared from 15 g. of Basic Blue 11 (CI. 44040),22 g. of glacial acetic acid and 1500 ml. of distilled water.

The fabrics were dyed at room temperature about 15 minutes, 40 C. forabout 15 minutes, and 60 C. for about 10 minutes. They were also dyedfor the period of time during which the temperature was being raised.This corresponded to a period of 20 minutes in going from roomtemperature to 40 C. and about 20 minutes in going from 40 C. to 60 C.

The samples were rinsed repeatedly in distilled water, then heated indistilled water 60 to C. changing water on several occasions. Thefabrics were then tumble dried. Inspection of the samples was then made.It was found that while the crosslinked control (catalyzed with a. metalsalt catalyst) :and untreated cotton were dyed a light blue, all thesamples in Table], whichhadbeen catalyzedwith hydroxy acids were dyed adeep blue. With a given acid, the samples had a deeper dye shade: astheamount of the acid inthe formulation increased. Morover, hydroxy acidswhich contained a-pheny'l' ringJIsuch as mandelic or tropic acid) dyed.an even deeper'shade of blue. J: a. 2 A portion of each sample was'thencutoff and laundered in a machine. After these samples weretumble dried,they again were inspected. The 'same'relation'ship's as had beenobserved previously still prevailed, namely, the untreated cotton andcrosslinked cotton were a light blue while the samples containingcarboxyl groups crosslinked into the fabric were a" dark'blue.

' AM L 1 v The same procedures were employed as in Examples: 1 and 2using the conventional'treatment (9% DMDHEU and 0.5% zincnitrate acidcatalyst), the acid catalyzed treatments (9% DMDHEU and from 2- 5%of-the acid catalyst) and untreated control" samples on mercerizedcotton fabric and on polyester-cottonblended fabrics. The results arelisted-in TableII an'dclearly demonstr'ate'thalt the use of the hydroxyacid catalyst leads to fabric with better tearing strength; "moistureregain and accessibility to basic dyes than does fabric given a'conventionaltreat ment.

0.5% zinc nitrate hexahydrate. The sample was dried for 7 minutes at 60C. and cured for 5 minutes at 160 C. Then an untreated sample of eachfabric was treated in a similar manner except that the zinc nitrate inthe finishing, formulation was replaced by. each-of the. followingcatalysts; 4% glycolic acid, 4% lactic acid, 4% mandelic acid, 4% malicacid, 4% citric acid, and 4% tartaric acid. These samples yieldedfabrics in which the glycolic, mandelic, malic, citric, lactic, andtartaric acids were grafted ;O11t0.th6 fabrics. The samples were thenwashed and tumble dried together with an untreated sample of eachfabric. Then, swatches of each fabric were placed in a dye bath preparedfrom 8 g. of 0.1. Basic Violet '1- (C.I. 42 5 and800 g. of distilledwater, and 20 drops of glacial acetic acid.

The-,,fab.rics were inserted at room temperature and hfi lr he.temperature raised to 95 C. at which point 100 cc. of distilled waterwere added to the bath. The bath was-then allowed -to cool slowly.After'that, the samples were removed; rinsed in distilled water severaltimes, then inserted inadistilled water bath several times. On oneoccasion thebath ,was raised to 40 C., the next bath, the temperaturewas raised to C., and with the next distilled water bath the temperaturewas raised .to -60 C. The sampleswere again rinsed several times indistilled water and tumble dried.

;;Inspe1ctionof the samples revealed that all samples containingcarboxyl groups were dyed a deep purple violet. By contrast, theuntreated samples or samples using a TABLE II.-PROPERTIES 0F BLENDEDFABRIgRT4TI%II 3RCERIZED FABRICS USING HYDROXY ACID Warp 00nd. tearingPercent WRA strength Percent moisture Dye Fabric Acid catalyst (deg.)(g.) COOH regain shade Mere. cotton 0.5% Zn (N 0;)2-6 H2O 304 580 0. 36. 2 Light blue. Do 3% glycolic acid.--.. 281 680 0.8 6. 3 Do. Do- 5%glycolic acid 281 700 1. 2 6. 2 Do. Do 2% malic acid 287 780 0. 5 Do.Do. 4% malic acid 282 720 0.8 6. 1 D0. D0. Untreated 172 1, 010 0. 2 7.2 Light blue. 150-50 polyester-cotton 308 513 0. 4 2. 1 Light blue.

Do 2% glycolic acid.. 307 663 0. 7 2. 9 Dark blue. Do- 3% glycolicacid.. 303 540 0. 8 2. 8 Do. D 5% glycolic acid. 303 553 0. 9 2. 9 Do.2% malic arid 312 560 0. 5 2. 7 D0. D0. 4% malic acid 810 538 0. 7 2. 6Do. Do Untreated 264 880 0. 2 3. 6 Light blue.

I Only cotton component dyed.

Swatches of the samples listed in Table I were inserted in 1%hydrochloric acid for a short period, then rinsed repeatedly indistilled water. Then the fabric was dipped in a dye bath prepared from10 g. of 0.1. Basic Violet 10 (CI. 45170), 5 cc. of glacial acetic acid,and 1000 ml. water. The fabrics were immersed in the dye bath at 40 C.,the temperature was raised to 60 C. over a period of 30 minutes, allowedto cool back to 35 C. during a period of 1 hour, 15 cc. of glacialacetic acid was added, temperature raised to 70 C. over a period of 30minutes, then allowed to cool to 50 C. The fabric was washed indistilled water, then tap water. After repeated Washing the samples wereinspected.

The crosslinked control with a metal salt catalyst was a pale pink, theuntreated control was a very light pink. On the other hand, the samplescatalyzed with glycolic acid, mandelic acid, citric acid, malic acid,lactic acid or tartaric acids were dyed a bright violet in color. Thesesamples provide another example of the fact that a basic dye can be usedto dye fabrics containing acid groups crosslinked into the fabric.

EXAMPLE 4 Three types of fabrics were employed in this experiment. Onewas an unmercerized all-cotton printcloth, a second was a mercerizedall-cotton printcloth, and a third was a 50-50 polyester-cotton blend.One sample of each fabric was padded with a solution of 9% DMDHEU andconventional crosslinking catalyst were dyed a pale violet. Thisrelationship held for the mercerized and unmercerized cotton series aswell as for the cotton-polyester series. In this respect, thecotton-polyester had its own peculiar shade changes due to the pooruptake of dye by the polyester component but relative relationshipsremained the same.

EXAMPLE 5 tumble dried. The sample prepared by crosslinking the fabricwith a zinc nitrate based catalyst was light blue, the untreated cottonfabric was a light blue while the fabrics utilizing the hydroxy acidcatalysts were dyed a dark blue. Examples of such acid catalystsincluded in this group were 4% tartaric acid, 6% citric acid, 5%glycolic acid, 6% lactic acid, 6% mandelic acid, 4% glycolic acid, 4%malic acid, 4% mandelic acid, and 3% tropic acid with 0.5% Zn(NO -6H O.The results from this ex- 7 periment clearly demonstrate that a saltpf'aibasic can be applied tocro ssl inked fabric, in which" a carboxylWeclaim; 1 -A process for imparting 10 a cellulo'sic textile"dinabIe-press performance and the quality'of being able/to respond toand accept basic dyes, the process comprising:

-(a) impregnating the eellulosid'textile Withaformula- Ition'c'onsisting of about from 1%jto 15 %-"of the cross- 4 linkingreagent dimethyloi dihydr'oxyethyleneu'rea and about'from 0.5% to10% ofan 1pha-h'ydroxy 'carboxylic acid selected from the group cofisitin'g ofcitric acid, glycol icl acid;' la"ctic acid, r'n'alicac'id,

- mandelic acid, mucic 1 acid, tartaric acid and; tropic acid;

- 3 (b) 'dryin'gfthe wet'imp'regnated textile for abouffrom '2 minutesto 24 hours, attemper'atureQabQrit from (c)- curing the dry impregnated'cellulosic' textile' -"at temperatures about from 100- tr -170"Clfor'periods of time about from 30 seconds to ZO- minpteS; using thelonger periods of time with the lower temperaf tures; then I ((1) dyeingthe cro'sslinked'textile with abasi'c dye;

iearboxylicwacid ismandelimwe w 1.. The process of: claim :1; wherein{the alpha-hydroxy carboxylic acid is mucic. .1

18.1 IIhej processgof r.claim- 1 wherein the alpha-hydroxy carboxy'licacidistartaric. v

. t r. ,9: 'iheprogess ofclairn-l wherein the alpha-hydroxy carboxy licaciiiis tropic. r I Y,

15 UNITED STATES PATENTS a 3,441,367 4/1969; Rierceyet al. 81852,950,553 8/1960 Hiirwit'zll; 8-185 j3,3114'107' 5,!3/519683 Cott0n'; 818 "3,4111,8 6O r11 /1968 Braunxetzalhee 8-18

